how the hell do you want to move the video/audio to different rooms?!?
The cost of a low-end client PC per display, vs. the cost of a single mid to high end system for multiple displays also needs to be weighed.
United Kingdom
Netgear do Powerline HD (That's their 200Mbps version)
Sorry I think you are confusing what "multi-threaded" means.
MP is multi-thread in that it makes use of more then one thread for processing tasks.
One issue you are going to face is that direct X doesn't support 3D acceleration for multiple displays.